Reinforced waterproofing sheet material



A1198, 1944. H. N. SANDELL 2,355,333

REINFORCED WATERPROOFING SHEET MATERIAL Filed June 17, 1943 2 Sheets-Sheet 1 INVENTOR ATTQRN .YS

Aug 8, 1944. H. N. SANDELL y 2,355,333

REINFORCED WATERPROOFING SHEET MATERIAL Filed June 17, 1943 2 Sheets-Sheetl 2 INVENTOFZ` '2. u u J `u i: Mywm at-ente'd Aug. 8, 1944 UNITED STATES PATENT OFFICE REINFOBCED WATEBPROOFING SHEET MATERIAL vHarry N. Sandell, Brookline, Mass., assigner to Sandell Manufacturing Company, Inc., Water-4 town, Mass., a corporation of Massachusetts Application June 17, 194s, serial No. 491,247

11 cram. (o1. 'iz-11s) material that is reinforced with an apertured` sheet-like metallic reinforcing member. It is a further purpose of this invention toprovide' areinforced waterproofing sheet material that can be used as a form for the molding or shaping of bodies comprising hydraulically setting cementitious material. It is a further purpose ot thisV invention to provide a reinforced waterproofing, f

ln'place in secured relation to the fibrous base sheet. while at the same time providing regions of substantial size wherein the apertured metallic sheet-like reinforcement may come into direct contact with' and become embedded in hydraulically setting cementitious material formed in contact therewith. Preferably the apertured metallic reinforcingV sheet material, in the regions between the spaced strips, is not secured or bonded to the base sheet so that in these regions the apertured sheet-likev metallic reinforcement is sheet material to which hydraulically setting ce` mentitious material may be applied and'to which' pose of this invention to provide a reinforced waterproofing sheet material that will remain permanently adherent to or embedded in formed hydraulically setting cementitious material as .a waterproofing membrane. It is a further purpose of this invention to provide a reinforced waterproong sheet material to which an hydraulically setting cementitious material may be directlyapplied and which will serve to some extent to reinforce the formed hydraulically setting cementitious material.

It is a feature of the reinforced,waterproofing sheet material of this invention that it comprises, combined in anovel way, a base sheet of fibrous sheet material and an apertured sheetlike reinforcing member, the fibrous base sheet being impregnated with a waterproofing material. According to this invention there -is combined with the fibrous base sheet and the apertured metallic sheet-like reinforcement. a plurality of strips of fibrous sheet material which are spaced substantially from each other and which are impregnated with waterproofing ma-` terial and which are bonded to the base sheet Vby waterproofing material through apertures in the apertured sheet-like metallic reinforcement. These spaced` strips of impregnated sheet material in combination with the underlying apertured sheet-like metallic reinforcement and brous back sheet afford a combination having a number of advantages.

The overlying spaced strips of fibrous sheet material provide positive means for securely' holding it will adhere tenaciously. It is a'further purand partly in another plane.

free to partially or even completely .become surrounded by and yembedded in the hydraulically setting cementitious material. Y-

It is a further feature of preferred embodiments of this invention that the reinforced waterproofing sheet material comprises essentially l throughout the extent thereof a bituminous waterproofing laye'r that is protected on both sides thereof by bitumen impregnated fibrous sheet material. A'I his bituminous waterproofing layer may be all in one plane or may be partly in one plane Thus advantageously4 the bituminous waterproofing that serves to -bond the spaced strips to the underlying base I sheet advantageously serves to provide such layer throughout the portion of the extent of the reinforced waterprooflng; sheet material occupied by said strips. The balance of the area of the reinforced waterprooflng sheet material that is not occupied by the spaced strips may advantageously have applied thereto spaced strips of bituminized sheet material which underlie the apertured sheet-like metallic reinforcement in the regions between' the strips and whichare bonded to the underlying base sheet by bituminous waterprooiing material, thereby providing a layer of bituminous waterproofing material that is between two bituminized' sheets and that complement the areas of the reinforced waterproofing sheet material occupied by the spaced strips of bituminized sheet material overlying the apertured sheet-like metallic reinforcement. In this manner a layer of bituminous waterproofing material is provided throughout the extent of the `reinforced waterproofing sheet material while the apertured 'sheet-like metallic reinforcement 55 leaving a substantial portion 'of the apertured sheet-like metallic reinforcement exposed for the purposes aforesaid and while utilizing a minimum of bituminized sheet material.

The reinforced waterproofing sheet material is useful fonmany purposes. Thus, for example, the reinforced waterproofing sheet material may be employed as a part of the forming surface of molds for making concrete bodies by securing the same to a suitable temporary framework so vthat the side thereof presenting the exposed apertured sheet-like metallic reinforcement is disposed for direct contact with the freshly poured or otherwise applied cement. Upon removing the temporary framework the reinforced waterproofing 4sheet material is left integrally united with the set concrete so as to provide a waterproofing surface. One typical use of such reinforced waterproof-lng sheet material is in the construction of arched concrete shelters or buildings wherein the concrete is poured onto molds carried by an arched supporting frame. By securing the reinforced waterproofing sheet material -to suitable spaced.

supports and applying the concrete to the up. per side thereof which presents the regions -of exposed portions of the apertured waterproong sheet material, a convenient and inexpensive form can be had which comprises the reinforced waterproofing sheet material as part of the mold for the concrete. After removal of the framework, the waterproofing sheet material remains as a waterproofing lining for the interior of the structure. While the reinforced waterproofing sheet material may 'sag somewhat between supports when the concrete is poured thereon, the sagging tends to provide a slightly corrugated configuration which adds to the ruggedness of the structure as a whole. Also the concrete tends to push the backing sheet slightly away from the apertured sheet-like metallic reinforcement, so that parts of the metallic reinforcement become embedded in the concrete, thereby not only causing 'the reinforced waterproofing sheet material as a whole to be firmly attached and adherent tothe concrete, but also reinforcing the concrete adjacent the surface thereof.

,The reinforced waterproofing sheet material may likewise be used as part of the forms for pouring foundations for buildings, either on the. inside or onthe outside or both, thereby providing an economical type of form and at the same time, by a single operation, providing one or more bituminous waterproofing layers in the wall. In a similar way the reinforced waterproofing sheet material-may be employed in other locations vof buildings and other structures wherever it is desired to provide a waterproofing sheet material integral.- with hydraulically set` cementitious material. If. desired, the reinforced of reinforced waterproofing sheet material con-v structed according to this invention.

Fig. 2 is' ay section of the reinforced water- 'proong sheet material taken on the line 2-2 of Fig. ,1with the thickness of the layers somewhat exaggerated for purposes of clarity.

Fig. 3 is a diagrammatic side elevation of apparatus of the manufacture of the reinforced waterproofing sheet material shown in Figs. 1 and 2.

Fig. 4 is a side elevation of the reinforced waterproofing sheet material shown in Figs. 1 and 2 as carried by set cementitious material, the thickness of the layers being exaggerated for clarity.

Fig. 5 is a sectional elevation similar to Fig. 2, I

Fig. 7 is a sectional elevation similar to Fig. 2,

but of another alternative embodiment of Waterprooiing sheet material constructed according to this invention and adapted to become integrally united on both sides thereof with the set cementitious material, and

Fig. 8 is a plan view of an alternative apertured sheetlike metallic reinforcement for use in reinforced waterproong sheet material embodying this invention.

Referring to Figs. l and 2, the brous sheet material preferably consists of a web of unspun cotton fibers, the web of fibers being impregnated with a bituminous waterproofing material as a binder. The web of cotton fibers is preferably composed of cotton fibers averaging about 1,/2 inch in length, the web being typical of a web of bers as produced by a conventional carding machine. Thin cotton batting or garnetting wadding may also be used. Ordinarily, the web material, considering the dry fibers by themselves, will weigh about 2-00 to about 400 grams per square yard. This sheet material of unspun cotton fibers may be initially impregnated with, for example, an asphalt having a softening point of about 135 F. to 145 F. and a penetration of Vabout 24 to 28.

Asphalt impregnated fibrous sheetmaterial of the character aforesaid is disposed in the rein- 'forcedwaterproong sheet material as a whole in different locations as follows. The reinforced waterproof-lng sheet material is provided with the continuous base sheet I0. lOverlying the base sheet I0 are the strips II of the asphalt impregnated sheet material, the strips II being bonded to thebase sheet by the layer I2 of the bituminous waterproofing material. Overlying the base sheet I0 and the strips II of the asphalt impregnated fibrous sheet material, is disposed the apertured sheet-like metallic reinforcement, which,- in the embodiment shown, is in the form of hexagonal open mesh wire netting I3. Overlying the wire netting I3 are spaced strips I4. Between the strips I4 andthe 'base sheet is disposed the vlayer I2" of bituminous waterproofing material in which the wires of the wire netting I3 are embedded and which serves to bond the strips I4 to the base sheet I0 through the apertures in the wire netting I3. Preferably the thickness of the sheet material in the structure as a whole coni form to the contours of the wires of the wire netting in the regions of the spaced strips I4. Preferably also the wire netting I3 in the regions between the strips I4 is not bonded to the base sheet I0 for reasons that will be explained below.

In the structure above mentioned it is preferable that the strips I4 be of sufficient width to overlap slightly the underlying strips II which' are in staggered relation with the spaced strips I4 as shown. Preferably also, and as shown, the regions between the spaced strips I4 where the apertured sheet-like metallic reinforcement is exposed, is substantially as wide as, or wider than.

the width of the strips Il. It is to be noted that in the structure above described, there is, throughoutthe extent of the reinforced metallic sheet material, a layer of bituminous waterproofing material between two layers of fibrous sheet material, this layer being provided by the layer I2 between the rstrips II and the base sheet I0 vand the layer I 2' between the strips Il and the base sheet I0.

A convenient apparatus for the manufacture of a reinforced waterproofing sheet material of the type shown in Figs. 1 and 2 is shown in Fig. 3.

' The roll I5 is a supply of previously bituminized sheet material of the lfull Width desired for the product. The sheet II) is taken from the roll I5 and is passed over guide roll I6 to the surface of the combining roll I1 which carries the sheet material to the nip between the combining rolls I1 and I1'. The asphalt for the layers I2 and I2 of bituminous waterproofing binder material is contained in a heat-liquifled condition in the tank I8 from which it is taken by the applicator layer 23 in the manner shown, the waterproofing sheet material ls made integral with the layer 26 and at the same time acts as a reinforcement for the surfaceof the layer 26 of cementitious material.

An alternative embodiment of this invention material. An apertured sheet-like metallic reroll I9 and is applied to the surface of the sheet III as the sheet I0 is passed from the guide roll II to the combining roll I1. Control of the amount of asphalt applied to the sheet III can be provided in any suitable way as by the doctor roll 20.

Strips II of bitumen impregnated sheet material are taken from the roll 2I, over the guide roll 22 and thence to the mp between the combining rolls I1 and I1. `The apertured sheet-like metallic reinforcement, such as the wire netting inforcement 29 overlies the'sheet 21 and strips l 30 overlie the'metallic reinforcement 29`and are bonded to the sheet 21 as byalayer 3I`of water-Y proong material, such as bituminous material. The strips 30 are spaced substantially-irolneach other so as to leave portions Tof .the metallic reinforcement 29 exposed. It is""t'.o be noted that in the embodiment of this invention shown in Fig. 4, there is a continuous 'layer of waterproofing material throughout the' lateral extent of the reinforced waterproofing sheetmateri'al.' In the drawings, the layer or sheetf'ltf-is shown of sub. stantial `thickness and may, ffo'r example, bev a' fibrous board-like sheet which acts asV dgsound, or heat-insulating material. I'n'this manner, a

waterproofing sheet material is provided: which c is adapted to become integral with an hydraulically setting cementitious Ymaterial in contactA therewith-and which provides a sound' orl heatinsulating layer as a perman rolls I1 and I1'. The strips Il of the bitumen I3, is taken from the roll 23, over the guide roll l material such as the layer 2l fmay be efx'nployeii` if 24 and thence to the nip between the combining 35 instead of the base layer Il of. the embqgimen j' of this invention shown in Fig. 2 or if desired a.,

impregnated sheet material are taken from the the embodiment of this invntion shqwm pigj'f roll 25 and thence 'to the combining roll I1' which carries the strips I4 to the nip between the combining rolls I1 and I1'.

It is apparent that upon simultaneuosly feeding the base sheet` I0, the strips II and Il and the wire netting I3, while maintaining their relative lateral positions as shown in Figs. l and 2,

the product as a whole is combined and made integrai at the nip between the combining rolls I1 and I1' as one operation.

In Fig. 4, the embodiment of the reinforced waterproof-lng sheet material shown in Figs. 1 and'2'is shown as integrally combined with an hydraulically setting cementitious material such as cement, plaster cr concrete. The component parts of the reinforced waterproofing sheet material are the same as shown in Fig. 2 and are indicated by like reference characters. the side of the reinforced waterproofing sheet material which has the apertured metallic reinforcement exposed is the cementitious layer 26.

It is to be noted that the cementltious material of the layer 26 has caused the base sheet I0 and the strip II of sheet material to become bowed slightly outwardly away from the wires of the wire netting I3 so that the wires of the wire netting I3 become `completely embedded and surrounded by the cementitious material of the layer 23. It is for-this reason that in the regions between the strips Il the apertured sheet-like metallic reinforcement is notV bonded to the base sheet of the waterproofing sheet material but is free to become spaced therefrom and embedded in the cementitious material when the cementitious sheet material is applied to the surface of the waterproofing shet material. It is appar- :nt that the wires of the wire netting I3 become Aembedded in the cementltious material of the '(5.

Applied tosheet or. layer of heatinsu1ating material.

2 may be made adherent, as by a bitui'ninous binder material, to a sheet or layer of heat insu.-

lation material by bonding the sheet Il .to the; l.

It is ordinarily preferable for the reasons above mentioned that the base sheet be arranged with; the other elements of the structure die reid-` throughouttheentire lateral extent of forced waterproong sheet material there will be a layer of waterproofing bituminous material or' the like disposed between impregnated nbrous sheets. This construction while preferable is not essential. Thus, in Fig. 6, there is shown an embodiment of this invention wherein the base lsheet consists of a single sheet 32 of'relatively heavy fibrous sheet material such as a bituminized felt. An apertured sheet-like metallic reinforcement 33 overlies thesheet 32 and spaced strips 3l are bonded to the sheet 32 by a layer 35 of suitable waterproong binder such as bituminous material.

1r desired, the reinforced .wdterprodnngsneer material may be made sojthat it may 'be in# tegral with a hydraulicallysetting cementitious` material disposed on bothfsides thereof. Such an embodiment of this inventionlls shownzlin Fig.

f 4fibers such as cotton fibers. sirable that the spaced strips which overlie the reason, it is preferable to have the spaced strips 30 andIB in staggered relation with respect to v each other and to have the strips 38 and 38' sufilciently wide so that they will slightly overlap on opposite sides of the sheet 36.

It is apparent that the embodiment of this,

invention that has been described hereinabove by way of example is subject to variation without departing from the scope of this invention. Thus, various types ofapertured metallic reinescasas rock wool, cellulosic synthetic fibers, proteinous synthetic bers, etc. When` the sheet material comprises unspun i'lbers,- lt is desirable that the fibers be long fibers, namely, averaging or more in length, it being preferable to employ fibers` 1/2" or .more in length. It is to be understood that any ber whether of cotton or other material that averages or more -in length is long" ber as this term is used herein.

When the sheet material comprises unspunfibers and a waterproofing binder, theweb material of unspun fiber usually runs to about 200 to 600 forcements may be used. One such alternative reinforcement is shown by way of example in Fig. 8 and consists of interwoven spaced wires. .40. Instead of a network of interwoven wires one set of spaced wires may merely overlie another set of spaced wires extending in a different direction from the rst set. Ordinarily, however, it is desirable to provide some sort ofinterwoven network since greater stability is achieved in this way. The wires that are used may 'be of any desired weight. and may, for example, be about 10 to 30`thousandths of an inch in diameter. Instead of using a network of wires, it is also possible to utilize an apertured metallic reinforcement which is formed fron: sheet metal which may, for example, be about 10 to 30 thousandths of an inch in thickness. Theapertures can be provided by punching the apertures out of the sheet metal or alternatively the apertures may be made so as "to produce the type of aper.; tured metallic sheet material which is commonly referred to as expanded metal. Ordinarily, the apertures in the apertured metallic reinforcement are about 1A. inch to 1 inch across although these limits are not essential in reinforced -waterproong -sheet materials embodying this invention.

With regard tothe sheet material, other fabrics and web structures may be utilized. For example, instead` of using a web or sheet of carded bers, unspun fibers such as long cotton may be combed or drawn so as to lie predominantly in one direction in a more or less parallel and straightened condition. By superposing web materials of this character with fiber direction in one web disposed at an angle to the fiber direction in another web, sheet materials of high tensile strength` and low Astretchability can be obtained. Ordinarily,

- however, fibrous webs of unspun long fibers as disposed by carding or the like, are preferable. Whether the fibers in the web or sheet material are carded, combed, drawn or the like, they are arranged in unspun relation so as to afford sheet material that has the capacity of conforming Yreadily to the wires or other solid portions of the apertured metallic reinforcement. It is preferable, therefore, to use throughout the entire reinforced waterproong sheet material of this invention bituminized sheets composed of unspun It is especially deanimal, vegetable, mineral or synthetic, such as y hair, wool, bast fibers, musa fibers, asbestos, glass, n

grains per sq. yd., and depending uponthe type of fiber employed the web usually runs about 2 to 6 diameters in thickness. However, brous web materials of unspun fibers maybe lighter or heavier Moreover, the web materials may. be unitary or may be composite, namely, composed of a plurality of laminations of the same or different materials. The amount -of waterproofing material that is employed in the webs of unspun fibers preferably is of the order of 300% and even as high as 750% of the weight of the fibers.

In ordinary practice asphaltic waterproong materials are preferred. Usually the softening point of a suitable asphalticwaterproong material runs from about 125 F. to about 175 F., the penetration running from about 20 to 30. In addition to asphaltic waterproofing materials, other bituminous waterproong materials may be employed, such as tars, pitches, etc. Moreover, other waterproong materials may be employed, such as natural or synthetic rubber, paraffin and other waxes, hydrogenated rosin, and other naval stores, etc. l

While itis preferable to employ sheet material composed of unspun fibers and a waterproofing binder, other/sheet materials maybe employed such as felt, paper, woven fabrics'and the like. As aforesaid, and especially for K the base sheet,

' the sheet material may be relatively thick, and

may be composed of fibrous material which acts as a heat or sound insulation material. It is not essential that the sheet material be as highly im- Sheet material in the form of a fabric made from in width ordinarily being preferable.

spun strands cannot be impregnated to as great extent as cana web of unspun long fibers. Accordingly, for effecting a. high degree of Waterproofness both from the point of view of transmission of water through the waterproong sheet material as a whole and from the point of view of protecting the bers of the fibrous sheet material, it is desirable to employ web or sheet material wherein unspun long bers are impregnated to a relatively high degree with a waterproofing binder.

In the reinforced waterproofing sheet material it is usually desirable that the spaced strips of impregnated brous sheet material be about 1V to 3 inches in width, strips about 1% to 1% inches As aforesaid the regions between the spaced strips wherein -the apertured sheet-like metallic reinforcement' is exposed, are desirably at least as wide as the width of the overlying strips and may, for example, be about 1 to 4 inches in width, with preferred construction being of the order of 11/2 to 3 inches in Width. As compared with the Width of the strips, the width of the regions between the strips usually is from 1 to 3 times the width of the strips.

` It is to be understood that the embodiments of escasas this invention that have been described herein have been setforth for exemplary purposes only 'and that the embodiments of this invention herein particularly described may be varied without 'departing from the scope of this invention as ment, said apertured metallic reinforcement between said strips 4being exposed in regions of substantial area f or direct contact with hydraulically setting cementitious material.

2. vA. reinforced waterproofing sheet material according to claim 1 wherein said apertured sheet-like metallic reinforcement is essentially unbonded to .said base sheet in said regions between said'spaced strips. 1

3. Reinforced waterproofing sheet material adapted' for contact application thereto of hydraulically setting cementitious material which comprises a base sheet ofbituminized fibrous sheet material,\an aperturedv sheet-like metallic reinforcement overlying said base sheet, and a plurality of spaced strips of bituminized fibrous sheet material overlying said metallic reinforcement and bondedI to said base sheet by bituminous waterproofing material through apertures in said metallic reinforcement, said apertured metallic reinforcement inthe regions between said spaced strips being exposed for direct contact with hydraulically setting cementitious material and being essentially unbonded in said regions to said base sheet, said regions between Y said spaced strips being at least substantially as wide as the width of said strips.

4. Reinforced waterproofing sheet material adapted for'contact application thereto of hy- -draulically setting comentitious material, which comprises a base sheet of fibrous sheet material impregnated with a bituminous waterproofing material, a first set of spaced strips of bituminized fibrous sheet material overlying said base sheet and bonded thereto by bltuminouswaterproofing material, and wire netting that overlies said base sheet and said first set of strips of bituminized fibrous sheet material, and a second set of spaced strips of bituminized brous sheet materia'l overlying said wire netting and in staggered relation to said first set of strips underlying said wire netting,` said second set of spaced strips ofv btiuminized fibrous sheet material being bonded to said base sheet by bituminous waterproofing material through the apertures in said wire netting, and said wire netting being exposed in the regions between the second set of spaced strips of bituminized sheet material for direct contact with hydraulically setting cementitious material.

5. A cementitious body integrally surface covered with waterproofing sheet material comprising spaced strips of apertured sheet-like metallic reinforcement embedded in the surface of said cementitious body, alternate strips of said apertured sheet-like metallic reinforcement being sheet on the opposite side of said apertured sheet-` embedded in bituminous waterproong material that bonds a plurality ofstrips of bituminized sheet material located between said cementitious body and said apertured sheet-like metallic reinforcement with a bituminized fibrous base like metallic reinforcement, said base sheet covering said lapertured sheet-like metallic reinforcement in the regions between said spaced strips of bituminized sheet material.

6. Reinforced waterproong sheet material adapted for contact application thereto of hydraulically setting cementitious material, which comprises a base sheet of fibrous sheet material impregnated with a waterproofing material, an apertured sheet-like metallic reinforcement overlying said base sheet, and aplurality of spaced strips of fibrous sheet material impregnated with a' waterproofing material and overlying said sheet-like metallic reinforcement and bonded to said base sheet by waterproofing binder mate- Irial through apertures in said metallic. reinforcement, said apertured metallic reinforcement between said strips being exposed in regions of substantial area' for direct contact with hydraulically setting cementitious material, and said base sheet being in the formof a web of unspun long fibers that is impregnated with a waterproofing material.

y 7. Reinforced waterproong sheet material according to claim 1 wherein said reinforced waterproofing sheet material comprises brous sheet material in the form of a web of unspun long cotton fibers impregnated to the extent of at least about 300% on the weight of the fibers with a bituminous waterproofing material.

8. .Reinforced waterproofing sheet material adapted for contact application to both sides thereof of hydraulically setting cementitious material, which comprises a base sheet of brous,

sheet material impregnated with a waterproofing material, an apertured sheet-like metallic reinforcement overlying each side ofsaid base sheet,

and a plurality of spaced strips of nbrous sheet material impregnated with a waterproofing material overlying each of said sheet-like metallic reinforcements and bonded to -said base sheet by waterproofing binder material through apertures in said metallic reinforcements, each of said aperturedmetallic reinforcements between said strips being exposed in regions of substantial area on both sides of said base sheet for direct contact with hydraulically setting cementitious material.

9. Reinforced waterproong sheet material according to claim 8 wherein said strips on op-` posite sides of said base sheet are disposed in staggered relation to veach other.

10. Reinforced waterproofing sheet material adapted for contact application thereto of hydraulicaliy setting cementitious material, which comprises a base sheet of fibrous sheet material impregnated with a waterproofing material, an apertured sheet-like metallic reinforcement overlying said base sheet, and a plurality of spaced strips of fibrous sheet material impregnated with a waterproofing material and overlying said sheet-like metallic reinforcement 'and bonded to said base sheet by waterproong binder material through apertures in said metallic reinforcement, said apertured metallic reinforcement between said strips being exposed in regions of substantial area for direct contact with hydraulically setting cementitious material, and said fibrous sheet material of said spaced strips being in' the form of a web of unspun long cotton fibers that is impregnated with a bituminous waterproong materiali1 11. Reinforced waterpu'oong sheet material adapted for contact application thereto oi hydraulically setting cementitious material, whichv comprises a base sheet of bituminous ilbrous sheet material, anapertured sheet-like metallic reinforcement overlyingsaid base sheet, a plurality of spaced strips of bituminized nbrous sheet material overlying said sheet-like metallic reinforcement and bonded to said base sheet through apertures in said metallic reinforcement by bituminous waterproofing material, said apertured reinforcement being exposed between said spaced strips, and further bituminized brous sheet materia.' underlying said metallic rein- 5 forcement and bonded to said base sheet by bituminous waterprooiing material throughout the areas of said waterproofing sheet material between said spaced strips thereby providing increased impermeability of said waterproong l0 sheet material in said areas between said spaced l strips as compared with the impermeability of said base sheet by itself in said areas.

HARRY N. SANDELL. 

